It is highly demanded to provide photographic materials having good original reproducibility and stable processing solutions and to simplify replenishment in the field of photoengraving to cope with the variety and complexity of prints.
Particularly, the originals in line work stage are prepared by inserting phototypeset letters, handwritten letters, illustrations and dotted photographs. Accordingly, images having different densities and line widths are included in the originals. Hence, it is highly demanded to provide process cameras, photographic materials or image forming methods which can finish these originals with good reproducibility. On the other hand, the enlargement of halftone photographs ("spread") or the reduction of halftone photographs ("choke") is widely carried out for the photoengraving of catalogs or large size posters. In the photoengraving wherein halftone dots are enlarged, the number of lines is roughened and dots which are out of focus are photographed. In the reduction, the number of lines/inch is increased in comparison with the original and finer dots are photographed. Therefore, image forming methods having a much greater latitude are required for keeping the reproducibility of halftone gradation.
Halogen lamps or xenon lamps are used as light sources for process cameras. Generally, photographic materials are subjected to orthosensitization to obtain photographing sensitivity to these light sources. However, it has been found that orthosensitized photographic materials are more affected by the chromatic aberration of lenses and hence image quality is liable to be deteriorated. This deterioration is remarkable with xenon lamps.
As a system for meeting the requirement for obtaining a large latitude, there has been proposed a method for obtaining a halftone image or line original having a high contrast and a high blackening density wherein the image area and the nonimage area are clearly distinguished from each other by processing lith type silver halide photographic materials comprising silver chlorobromide (having a silver chloride content of at least 50%) with hydroquinone developing solutions containing sulfite ion at a very low effective concentration (usually not higher than 0.1 mol/liter). However, since the concentration of sulfite in the developing solutions is low in this method, the solutions are unstable against oxidation by air. Various attempts have been made to preserve the activity of developing solutions but these have resulted in very slow processing speeds and low working efficiencies.
Accordingly, there have been proposed image forming systems which solve the problems of unstableness in the formation of image by the above-described development method (lith development system), enable development to be carried out with processing solutions having good storage stability and give high contrast photographic characteristics. For example, U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,600 and 4,311,781 disclose systems wherein surface latent image type silver halide photographic materials containing specific acylhydrazine compounds are processed with developing solutions having a pH of 11.0 to 12.3, containing a sulfite preservative in an amount of at least 0.15 mol/liter and having good storage stability to form ultrahigh contrast negative images having a gamma (.gamma.) value exceeding 10. These new image forming systems have such characteristics that silver iodobromide as well as silver chloroiodobromide can be used, while only silver chlorobromide having a high silver chloride content can be used in conventional ultrahigh contrast image formation.
Though the above-described image forming systems have excellent performance with regard to the quality of sharp halftone dots, processing stability, quickness and the reproducibility of the original, it is highly demanded to provide systems wherein the reproducibility of the original and processing stability are further improved to cope with the increasing variety of types of prints.
Systems using hydrazine compounds, which contain redox compounds releasing development inhibitors when oxidized, are disclosed in JP-A-61-213847 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application") and JPA-64-72140.
However, it has been found that the dependence on these methods of development is not preferred.